Pin-type synchronizer mechanisms for use in multi-ratio transmissions are well known. Such mechanisms include friction and jaw members for respectively synchronizing and positive clutching a gear to a shaft, a plurality of pins rigidly extending from at least one friction member and through openings in a radially extending shift flange, pre-energizer assemblies for engaging the friction members in response to initial engaging movement of the flange, and blockers defined by shoulders on the pins and about the flange openings for preventing asynchronous engagement of the jaw members.
It is also known in the multiple ratio transmission art that synchronizer mechanisms may be used to reduce shift time of all or some of the transmission gear ratios. It is also known that the shift effort required by a vehicle operator, i.e., force applied to a shift lever, may be reduced by use of synchronizer mechanisms of the self-energizing type. Since operator shift effort generally increases with vehicle size and weight, synchronizer mechanisms of the self-energizing type are especially important for heavy duty trucks. U.S. Pat. No. 5,092,439, which discloses a pin-type synchronizer of the self-energizing type, is incorporated herein by reference.